RESTEasy does not give priority to application provided MessageBodyWriters and uses built-in providers instead.

When I create a custom MessageBodyWriter for my entity that produces text/plain MIME type my MBW is not used. Looks like built-in toString() method-based provider is used instead. I think this is a bug since it conflicts JAX-RS specification that says that application-provided providers must be used in preference to built-in providers when either can handle the request.

Issue can be reproduced on following trivial example:

public class User {

private String username;
private String email;

public User() {
}

public User(String username, String email)

{ this.username = username; this.email = email; }

public String getUsername()

{ return username; }

public void setUsername(String username)

{ this.username = username; }

public String getEmail()

{ return email; }

public void setEmail(String email)

{ this.email = email; }

}

@Path("/user")
@Produces("text/plain")
public class UserResource {

private static final User user = new User("jharting", "email@example.com");

@GET
public User getUser()

{ return user; }

}

@Provider
@Produces("text/plain")
public class UserBodyWriter implements MessageBodyWriter<User> {

public long getSize(User arg0, Class<?> arg1, Type arg2, Annotation[] arg3,
MediaType arg4)

{ return getStringRepresentation(arg0).length(); }

public boolean isWriteable(Class<?> arg0, Type arg1, Annotation[] arg2,
MediaType arg3)

{ // return arg0.equals(User.class) && arg3.equals(MediaType.TEXT_PLAIN_TYPE); return true; }

public void writeTo(User arg0, Class<?> arg1, Type arg2, Annotation[] arg3,
MediaType arg4, MultivaluedMap<String, Object> arg5,
OutputStream arg6) throws IOException, WebApplicationException

{ BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(arg6)); bw.write(getStringRepresentation(arg0)); bw.flush(); }

private String getStringRepresentation(User user)

{ return user.getUsername() + ";" + user.getEmail(); }

}